1. Field of the Invention
The invention concerns the field of medical technology and pertains to a device for the anchoring of a suture in tissue, for instance in bone tissue.
2. Description of Related Art
The anchoring of sutures in human or animal bone tissue is used in techniques for medical and veterinary procedures, for instance for re-attaching of tendons and ligaments in the vicinity of joints. The bone in which this anchoring is undertaken has a dense outer layer (cortical bone), having a thickness on the order of 1 to 2 mm, and on the inside turning into of less dense bone tissue (spongiosa, or cancellous bone). Depending on the patient, the cancellous bone can have very different properties, in particular, depending on the age and health of the patient, this bone can have very different mechanical stability and regenerative ability.
According to the state of the art, various screw-shaped anchors are used for the anchoring of sutures in bone tissue. These screw-shaped anchors are inserted into bore reaching e.g. through the cortical bone and, if the cancellous bone has only little mechanical stability, their hold in the bone tissue relies primarily on the cortical bone. Radially compressible anchors are also used for the anchoring of sutures in bone tissue. These anchors are equipped with, for instance, deformable barbs and are inserted through the cortical bone into the cancellous bone, where the barbs expand and/or catch, depending on the mechanical resistance offered by the cancellous bone. These anchors are impacted into the bone tissue, for example, through bores provided at least through the cortical bone. A third known approach to anchoring sutures is to pre-drill an opening at least through the cortical bone, insert the anchor through the opening into the cancellous bone and, usually with the help of the suture, turn the anchor approximately 90 degrees. As the anchor is longer than wide, the turning brings the anchor into an orientation in which it can no longer be extracted through the pre-drilled opening and is therewith anchored in the cortical bone. The publications WO 02/069817, WO 04/017857 and WO 05/079696 disclose further anchoring procedures, which are suitable for the anchoring of sutures in tissue. The disclosed procedures rely on the liquefaction of a thermoplastic material via the application of mechanical vibrations, for instance ultrasonic vibrations, wherein for such liquefaction, friction between the bone tissue and the thermoplastic material and therewith a minimal mechanical strength of the tissue is needed.
The attachment of sutures to state of the art suture anchors is achieved, for example by the use of proximal eyelets, wherein anchors and eyelets are designed such that the implanted anchor does not protrude above the bone surface and the suture can pass freely through the eyelet after the implantation of the anchor. If a such anchored suture is to be used for the attachment of a tendon or ligament and is to cut into the bone tissue as little as possible, it is advantageous that the suture be attached to the anchor as near as possible to the bone surface. With respect to the suture anchors, it is also desirable that the strength of the anchorage corresponds to the strength of the eyelet and the suture. Anchor cross sections on the order of 5 mm or smaller are desirable, not only for application in minimally-invasive surgery, but also for allowing small pre-drilled bores in the bone tissue such that anchors can be implanted at small distances from each other. Furthermore, it is desirable for the surgeon to be able to place the anchor using only one hand.
The known suture anchors described above are usually designed for specific anchorage locations and also for specific bone qualities, not least because the known anchorage principles are not very widely applicable. This means that the surgeon must select one or another type of anchor for each operation, or even multiple types of anchors must be used for a single operation.